A mathematical analysis of the expected short-circuit current density in Schottky-barrier solar cells is presented. For a solar cell with the Schottky barrier on the bottom, back illuminated, the active semiconductor material, GaAs for this example, must be a thin film for maximum efficiency. A comparison between this cell and a single-crystal solar cell with the Schottky barrier on the top, front illuminated is made. This comparison shows that solar cells made from polycrystalline films could deliver the same short-circuit current as a single-crystal solar cell provided that the minority-carrier diffusion length in the polycrystalline films can be kept to within one order of magnitude lower than that for the single-crystal material. The reason for this is that solar-reflection losses for the back-illuminated thin-film cell can be minimized, while for the front-illuminated single-crystal cell the losses must always be high.